所以当我把我的OptionsViewController作为AppDelegate didFinishLaunchingWithOptions中的rootViewController时...

let rootVC = OptionsViewController()
        let navigationController = UINavigationController(rootViewController: rootVC)
        navigationController.navigationBar.barTintColor = .white
        navigationController.navigationBar.isTranslucent = false
        navigationController.navigationBar.tintColor = .black
        self.window = UIWindow(frame: UIScreen.main.bounds)
        self.window!.rootViewController = navigationController
        self.window?.makeKeyAndVisible()

...如果我在viewDidLoad()中这样做，设置OptionViewController的标题就可以工作：

title = "Route Options"

但是当我把OptionsViewController推到导航栈上时，标题没有显示。
例如，如果我在AppDelegate中启动不同的视图rootViewController：

let rootVC = HomeViewController()
    let navigationController = UINavigationController(rootViewController: rootVC)
    navigationController.navigationBar.barTintColor = .white
    navigationController.navigationBar.isTranslucent = false
    navigationController.navigationBar.tintColor = .black
    self.window = UIWindow(frame: UIScreen.main.bounds)
    self.window!.rootViewController = navigationController
    self.window?.makeKeyAndVisible()

在HomeViewController中，我像这样推送OptionViewController：

let optionsVC = OptionsViewController()
    navigationController?.pushViewController(optionsVC, animated: true)

标题不显示!

我管理标题显示的唯一方法是执行（在OptionViewController中）

navigationController?.navigationBar.topItem?.title = "Route Options"

但它显示为后退按钮而不是中间，这不是我想要的。

如果有人能告诉我如何设置标题，使其在推送到navigationcontroller堆栈时位于导航栏的中间，那就太好了!

代码

• • 应用代理. swift**

class AppDelegate: UIResponder, UIApplicationDelegate {
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        let rootVC = HomeViewController()
        let navigationController = UINavigationController(rootViewController: rootVC)
        let barAppearance = UINavigationBar.appearance()
        barAppearance.barTintColor = UIColor.blue
        barAppearance.tintColor = UIColor.white
        barAppearance.titleTextAttributes = [NSForegroundColorAttributeName: UIColor.white]
        self.window = UIWindow(frame: UIScreen.main.bounds)
        self.window!.rootViewController = navigationController
        self.window?.makeKeyAndVisible()

        return true
    }

• • 主页视图控制器. swift**

class HomeViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, DestinationDelegate {
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
            let optionsVC = OptionsViewController()
            self.definesPresentationContext = false //else going to try and present optionVC on homeVC when in optionVC
            navigationController?.pushViewController(optionsVC, animated: true)
        }
        tableView.deselectRow(at: indexPath, animated: true)
    }
}

• • 选项视图控制器. swift**

class OptionsViewController: UIViewController, UITableViewDelegate, UITableViewDataSource,
    DestinationDelegate, SearchBarCancelDelegate,UISearchBarDelegate,
    CLLocationManagerDelegate {
    override func viewDidLoad() {
        self.title = "Route Options"
    }